Taxon identifiers are identifiers assigned to biological taxon by biological and taxonomic databases for purposes of establishing a point of reference for each catalogued taxon. Assigning a taxon with a permanent identifier such as a string of numbers allows for information such as taxonomic classification to be updated without affecting the ability to retrieve or reference the data of the respective taxon. A taxon identifier works in much the same way that a barcode is used to retrieve data about an item of interest. When used on Wikipedia, taxon identifiers can be found near the bottom of Wikipedia pages, linking to records on taxonomic databases. In many cases, each taxon name in a taxonomic database has a unique identifier, although this is not always the case. (For example, the International Plant Names Index regularly has multiple identifiers for a taxon name, often but not always of the form N-1, N-2, etc.)

Taxon identifiers enable researchers to search more easily for pertinent information on the subject of an article, without needing to disambiguate the subject manually. For example, taxon identifiers are used in species articles so that the information in the article can be easily cross-referenced with the popular Catalogue of Life database.

More generally, taxon identifiers are a method of creating and maintaining index terms for bibliographical material. The links produced by the {{Taxonbar}} template on Wikipedia go to taxon information pages of online biological or taxonomic databases. As an example, the Wikipedia taxon bar information for Sequoiadendron giganteum looks like this:

NCBI: Taxon Browser from the National Center for Biotechnology Information

Plant List: The Plant List, a list of botanical names of species of plants created by the Royal Botanic Gardens, Kew and the Missouri Botanical Garden

PLANTS: Natural Resources Conservation Service, a database from the United States Department of Agriculture (USDA) that provides technical assistance to farmers and other private landowners and managers

Tropicos: Tropicos, an online botanical database containing taxonomic information on plants, mainly from the Neotropical ecozone (Central, and South America)

WCSP: World Checklist of Selected Plant Families , an international collaboration that provides the latest peer reviewed and published opinions on the accepted scientific names and synonyms of selected plant families.

This is a small subset of available databases, and these links will vary from taxon to taxon depending on its type and the availability of database entries.